Aluminum compounds as a management tool for Eutrophic Lakes: State of the art

Chemical applications in eutrophic lakes, known as geoengineering interventions, have been utilized for decades. This review provides an overview of the applications of aluminum compounds for lake rehabilitation based on numerous case studies obtained through a systematic search methodology. The results reviewed indicate that, given appropriate doses, aluminum compounds have generally proven effective in reducing the internal phosphorus load and preventing cyanobacterial blooms. However, it is important to acknowledge certain limitations and cases where undesired effects have been detected (such as acidification and fish mortality), emphasizing the need to design off the applications carefully. Polyaluminum chloride (PAC) is preferred mainly due to its higher pH buffering capacity, flocculation efficiency, and avoidance of sulfate addition and interference in sulfur cycles. Dose calculation should be based on the internal load criterion, with limitations on the amount dosed in each application. Direct application in the water column is the most reported methodology and has shown logistic advantages. Climate and weather knowledge are relevant for defining timing. However, varied treatment efficiencies have been reported, so it is necessary to conduct comprehensive pre-application experiments. It is also recommended to include mesocosm-scale testing as a preliminary stage before applying treatments to the entire lake. The review also discusses the effects on water characteristics, the factors that affect the efficacy and longevity of applications, and the use of aluminum compounds in combination with other substances for ballasting or capping purposes. Furthermore, the interaction of such treatments with biota is also considered. We conclude that the intervention strategy should consider the systemic and functional perspective, as well as each lake's characteristics. The lake-specific nature of aluminum treatments underscores the importance of characterizing individual lakes before designing applications or extrapolating results to other systems.